1.7 Enzyme action + 1.8 Enzyme denaturing + 1.9 Changing enzyme activity

Question 1

What is an enzyme?

Answer 1

A biological catalyst that increases the rate of reaction in living organisms

Question 2

What is a catalyst?

Answer 2

A substance that increases the rate of reaction without being used up

Question 3

Factors of an enzyme

Answer 3

• Present in many reactions, allowing them to be controlled
• Can both break up large molecules and join small molecules
• They are protein molecules and the shape of the enzyme is vital to its function. This is because each enzyme has its own uniquely shaped active site where the substrate binds.

Question 4

How do enzymes work?

Answer 4

The Lock and Key hyperthesis:

1- The shape of the substrate is complementary to the shape of the active site, so when they bond it forms an enzyme substrate complex.

2- Once bound, the reaction takes place and the products are released from the surface of the enzyme.

Question 5

How do enzymes catalyse (speed up) a reaction?

Answer 5

They bind to a substrate that has a complementary shape, as this is the only way that the substrate will fit into the active site - This is called enzyme specificity

Question 6

What do enzymes require to catalyse (speed up) the rate of reaction?

Answer 6

• Optimum temperature
• Optimum pH
• Optimum substrate concentration

Question 7

What is the optimum temperature in humans?

Answer 7

Around 37 degrees

Question 8

How does temperature affect enzymes/ rate of reaction?

Answer 8

• The rate of reaction increases with an increase in temperature up the optimum temperature. If the temperature goes above it optimum, the temperature will rapidly increase and the reaction with eventually stop.
• When the temperature becomes too hot, the bonds that hold the enzyme together will begin to break.
• This changes the shape of the active site, so the substrate can no longer ‘fit into’ the enzyme.
• The enzyme is said to be denatured and can no longer work.

Question 9

What is the pH of most enzymes?

Answer 9

7 (neutral) - but some that are produced in more acidic conditions have a lower optimum pH

Question 10

How does pH affect enzymes/ rate of reaction?

Answer 10

• If the pH is too high or too low, the forces that hold amino acid chains that make up the protein will be affected.
• This will change the shape of the active site, so the substrate can no longer fit in.
• The enzyme is said to be denatured and can no longer work.

Question 11

What is substrate concentration?

Answer 11

Concentration of the substance binding to the enzyme

Question 12

How does substrate concentration affect enzymes/ rate of reaction?

Answer 12

• As substrate concentration increases, the rate at which enzyme-substrate complexes can be formed increases.
• This only occurs to a point (the saturation point) and increasing the substrate concentration above this will have no effect on the rate of reaction. The saturation point is different for every enzyme.